Context: While industrial use of UML was studied intensely,little is known about UML use in Free/Open Source Soft-ware (FOSS) projects. Goal: We aim at systematically mining GitHub projects to answer the question when mod-els, if used, are created and updated throughout the whole project’s life-span. Method: We present a semi-automated approach to collect UML stored in images, .xmi, and .uml ﬁles and scanned ten percent of all GitHub projects (1.24million). Our focus was on number and role of contributors that created/updated models and the time span during which this happened. Results: We identiﬁed and studied 21 316 UML diagrams within 3 295 projects. Conclusion: Creating/updating of UML happens most often during a very short phase at the project start. For 12% of the models duplicates were found, which are in average spread across 1.88 projects. Finally, we contribute a list of GitHub projects that include UML ﬁles.

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